The invention relates to improvements in methods of and in implements for cutting or trimming books and/or similar stacks of overlapping sheets. More particularly, the invention relates to improvements in methods of and in implements for removing surplus material from selected sides of stacks of overlapping sheets of paper or the like.
The quality of treatment of the backbone of a book is of considerable importance for the acceptability of the finished product, be it a magazine, a brochure, a pamphlet or a book (hereinafter book for short). Thus, satisfactory treatment of the backbone can prolong the useful life of the book. For example, if the backbone is to be adhesively secured to the corresponding portion of a book cover, a cutting or trimming treatment which involves withdrawal of fibers from the backbone can enlarge the area of contact between the cover and the treated side of the book. An additional important requirement is the accuracy of treatment, i.e., the exact dimensions of the product which is left subsequent to cutting or trimming. As a rule, a stack of sheets (such as an accumulation of signatures which are to form the pages or sheets of a book) is confined between two clamps or between the jaws of tongs and is transported, as one of a series of such stacks, along a predetermined path through a trimming or cutting station. The clamps or jaws (hereinafter clamps) must grasp the two outermost sheets of the stack without any slippage; at the same time, the clamps should not exert an excessive pressure against the adjacent sheets because this could result in the development of a mushroom-like outwardly bulging portion (signature folds) at the backbone and would necessitate removal of a larger quantity of material by the cutting or trimming implement. Removal of the outwardly bulging portion results in unsatisfactory configuration of the trimmed backbone and in a reduction of the effective area of the trimmed side with attendant establishment of a relatively weak connection between the thus treated side and the cover. Moreover, unsatisfactory cutting or trimming of the backbone of a stack of signatures can affect the appearance of the finished book.